Heater



Oct. 9, 1945.

F. O. HESS HEATER Filed Sept. 29, 1941 2 Sheets-Sheet l INVENTOR FfiEDE/Wc O. HEss ATTORN I V F. O HESS HEATER Filed Sept. 29, 1941 2 Sheets-s t 2 m H R. c mm M E R F Patented "Oct. 9, 1945 HEATER Frederic 0. Hess, Germantown, Pa., asslgnor to Selas Corporation of- America, a corporation of Pennsylvania Application September 29, 1941, Serial No. 412,778

6 Claims. (Cl. 158-96) The general object of the present invention is to provide an improved fuel burning air heater which is especially useful for airplane heating. More specifically, the object of the invention is to provide a small, compact, light-weight heating unit of novel type and characterized by its simple construction and its operative reliability. A further object of the invention is to provide a heating unit of such small size and weight as bustion air.

In a preferred form of the invention, the gasolene vaporizing and air and vapor mixing means comprises a body of porous ceramic material, through the pores of which gasolene is moved by capillary action to extended vaporizing surface portions of the body over which the combustion air is moved into a combustion chamber in which the mixture of air and vaporized gasolene is burned.

However, I may employ other means for moving gasolene by capillary action to an extending vaporizing surface swept by the combustion air. For example, the ,vaporizer may be formed of metal laminae, with the gasolene moved by capillary action through the joints between the laminae to suitably extended vaporizing surfaces, which may be formed by the walls of slots or grooves extending through the laminated mass transversely to the lamination planes.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, however, its advantages, and specific objects attained with its use, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described a preferred embodiment of the invention.

Of the drawings:

Fig. 1 is a sectional elevation of a heating unit embodying the invention;

Fig. 2 is a partial section on the line 2-2 oi Fig. 1;

Fig. 3 is a partial section on the line 3-3 of Fig. 1:

Fi 4 is a sectional elevation of a heating unit of modified form;

Fig. 5 is a section on the line 5-4 of Fig. 4;

Fig. 6 is an elevation in section of a portion of the apparatus shown in Fig. 4;

Fig. 7 is a section taken similarly to Fig. 5. illustrating a modification of the heating unit shown in Figs. 4 and 5; and

Fig. 8 is a partial sectional elevation illustrating a modified form of gasolene vaporizer.

The heating unit shown in Figs. 1 to 3 includes a vertically disposed body A comprising a tubular outer wall portion A surrounding an annular air space B and comprising an inner tubular wall portion A surrounding a central heating space or chamber C, and separating the latter from the air space B. The tubular walls A and A of the member A are connected by longitudinal ribs or webs A extending radially across the air heating space B, and forming heat dissipating fins.therein. Longitudinal ribs or fins A extend radially inward from the wall A. Advantageously, the tubular walls A and A and ribs or fins A and A form integral portions of a single die-casting of brass or other suitable metal.

Detachably connected to the lower end of the body A is a lower end member D, which may be a die-casting of zinc or aluminum, and encloses a fan or blower chamber. An exhaust fan rotor E is mounted in said fan or blower chamber. The rotor E draws hot products of combustion from the lower end of the chamber C and discharges them through an outlet D which may lead to the external atmosphere. The rotor E is driven by an electric motor enclosed in a lower housing portion F of the member D. As shown a portion of the top wall of the chamber in which the rotor E is mounted, is formed by an integral flange portion A of the member A.

Detachably connected to the upper end of the body A is an upper end member G, comprising a tubular wall portion in end to and relation with portion surrounded by a tubular boss portion C1 of the member (3'. The boss is coaxial with the opening G and in the assembled condition y of the unit is coaxial with the body A.

A cup shaped member H has its upper end telescopically received in the outlet G of the air passage 6 and is formed at its underside with an annular recessed seat H receiving the upper edge of the wall A. As shown, an annular gasket or packing h, which may be formed of asbestos, is interposed between the member H and the wall A. A multiplicity of small burner orifices or passages H extend through the bottom wall of the member H. The latter is advantageously formed of a suitably dense nonporous ceramic material adapted to withstand high temperatures, and the bottom wall of the member H with its orifices I-F thus forms a burner wall of the well known type disclosed in my prior Patent No. 2,103,365 granted December 28, 1937.

A body I of circular outline and formed of porous ceramic material is mounted in the upper portion of the cup shaped member H, and forms a ported wall interposed between the combustion air supply passage G and an air and gasolene mixing space 2 between the member I and the bottom wall of the member H. An axially extending well I is formed in the member I with its closed lower end some distance above the under surface of the member. The open upper end of the well I is enlarged to receive a rubber bushing J, surrounding the boss G and forming a resilient seal against leakage through the joint between the boss G and the member I. The bushing J also serves as an elastic cushion connection between the parts G and I, adapted to accommodate relative thermal expansion and contraction movements of those parts. The member I is formed with ports for the passage of air from the supply passage G to the mixing space i. Those ports comprise a plurality of kerfs or slots I formed in the member I at its periphery, and a plurality of small diameter passages 1 formed in an annular portion of the member I between the slots F and the well 1'. Central portions 1 and I of the top and bottom surfaces of the porous body I are advantageously glazed to prevent those surface portions from being wetted by gasoline flowing to said surfaces from the well I through the pores of the body I.

To prevent back fire through the passage G the latter may advantageously include a fire screen K, which may be formed in the usual manner of layers of wire cloth or of thin corrugated or perforated metal sheets. As shown, a damper L is mounted in the passage G for throttling adjustment of the air flow through said pasage. The damper L may be adjusted to reduce the air flow in starting the heater into operation so as to insure a rich ignitable fuelair mixture in the space i at that time. The damper L may also be adjusted manually or automatically to compensate for the effect of changes in atmospheric pressure due to changes in the airplane altitude. However, as disclosed in my prior application, Serial No. 409,439 filed Sept. 4, 1941, if the motor F is energized by a source of constant E. M. F., it will tend to maintain a constant flow of products of combustion away assume from the combustion chamber C, notwithstanding variations in the pressure of the atmosphere from which air is drawn into the chamber through the passage G. Means responsive to atmospheric pressure for automatically adjusting a damper to variably throttle combustion air fiow on variations in airplane altitude are disclosed in my said prior application Serial No. 409,439, and in my earlier application Serial No. 348,324, filed July 29, 1940. In my said application 409,439, I have also disclosed means for making automatic adjustments in the combustion air supply means to compensate for changes in atmospheric temperature.

As shown, the air to be heated is drawn into the lower end of the air space B from the atmosphere enveloping the heater, by a circulating fan including a rotor M mounted in a fan casing M detachably connected to the upper end of the end member G. The outlet M of the fan casing.

M may open directly into the space in which the heater is located in some cases, and in others may be extended to form, or may be connected to, a conduit for conveying the heated air to a place of use at some distance from the heater.

As shown the casing M is formed with a central opening in its under side receiving an annular top flange portion G of the end member G which forms the major portion of the under wall of the chamber for the rotor M.

The housing N for the electric motor riving the rotor M is preferably an integral portion of the casing M. If and when necessary the housing N and also the previously mentioned housing F may be split to facilitate the incorporation of the corresponding motor therein.

As shown the adjoining pairs of heater shell parts A and G, A and D and G and M, have over-lapping portions detachably secured together by clamping bolts 0..

The apparatus shown in Fig. 1 includes an ignition device of the hot wire type comprising an electric heating wire P mounted in a tube P. The tube P may well be formed of a metallic alloy adapted to withstand high temperatures, extends through the walls A and A to the heating space C, at a level suitably close to the underside of the burner wall bottom of the member H. The wire P may be energized to maintain its ignition temperature continuously while the heater is in operation, but ordinarily it needs to be energized only to start the heater into operation, as the ignition may thereafter be maintained by the burner wall which in normal operation is heated to incandescence.

In accordance with the present invention, the porosity, form and dimensions of the member I are designed for the capillary flow of gasolene from the well I through the pores of the body I to the walls of the ports I and I and thence into the streams of combustion air moving through those ports, as required to maintain the desired rate of combustion for which the unit is designed.

The air sweeping over the walls of the ports P and P vaporizes gasolene coming to those walls, and entrains the gasolene vapors. The air and vapor mixing action thus initiated in said ports is completed in the chamber 2', from which a suitably uniform combustible mixture passes through the different burner orifices H into the upper region R of the heating space C wherein combustion is initiated and maintained by the hot wire P and hot burner orifice wall formed by the bottom of the member-H.

It will now be understood that a multiplicity of gas streams issue from the lower ends of the orifices H and it is at this region that the burner flames are produced and maintained. By producing a plurality of small gas streams, efilcient combustion is obtained and substantially complete combustion is effected at the upper region R of the heating space C. From the upper region R. the heated products of combustion pass downwardly through the heating space C and are withdrawn from the lower end thereof by the rotor E and discharged through the outlet D An advantageous characteristic of the invention is that the gasolene m the well 1' need not be at a pressure significantly above the pressure of the atmosphere from which combustion air is drawn into the heater. In consequence, the gasolene may pass through the member I by gravitational flow from some portion of the airplane engine fuel supply system when the relative disposition of said system and the heater permits, as it will in many cases. In other cases, a special gasolene pump having a discharge pressure of one half pound per square inch or so may be employed to supply gasolene to one or more heating units.

The practical merit of the heating unit shown in Figs. 1-3 is enhanced by the relative ease with which the heating unit may be assembled and disassembled for cleaning, repairs-or part replacements.- The formation of the four parts A, D, G and M, which collectively form the metallic shell portion of the unit, as die-castings, insures the accuracy in their form required for their ready and interchangeable assemblage with one another and with associated parts. Moreover, the few additional heater parts, including the molded ceramic parts H and I, fan rotors and their driving motors, the fire screen K, damper L, and ignition device, are all adapted for quantity production with the accuracy needed for interchangeable use of the different parts. In consequence, it is readily feasible to maintain numerous more or less widely distributed stocks of heater replacement as required for the maintenance of the heaters of military airplanes in operative condition under war conditions.

The inherent compactness and unusually small bulk and weight of a heating unit required for a given heating effect will be readily apparent to those skilled in the art. Merely by way of illustration and example, I note that a heating unit formed and proportioned as shown in Figs. 1 to 3, weighing about ten to twelve pounds in which the inside diameter of the tubular wall A is about four inches, is adapted to liberate heat at the rate of about 10,000 B. t. u.'s per hour.

As will be apparent, the general features and advantages of the-heating unit shown in Figs. 1-3, may be incorporated in and obtained with constructions of various forms; and, by way of example, I have shown one modification of the invention in Figs. 4 and 5, and a second modification in Fig. '7. The unit shown in Figs. 4 and 5 comprises a tubular body member AA corresponding generally to the previously described body member A but differing from the latter in that it does not include the continuous tubular outer wall A of the member A, and in that its heat dissipating fins or ribs A are in the form of external circumferential rib portions of the wall A. In the form shown in Figs. 4 and 5, the

air to be heated is moved through the spaces between the ribs A by a circulating i'an MA, which with its driving motor NA, is located at one side of the member AA with its axis generally transverse to the axis of the member AA and approximately midway between the ends oi! the latter. The air discharged by the fan MA is caused to move in suitably close contact with the wall A and the fins A of the member AA through a passage formed by easing parts Q at opposite sides of, and partially enveloping the circumferentially extending rib A The casing parts may be integral portions of the die cast body AA, or may be thin sheet metal parts brazed or welded to or otherwise secured against th peripheral edges of the fins A. A

In the unit shown in Figs. 4 and 5, the upper end member GA is a tubular body coaxial with the body AA and-having-its lower portion fitting snugly about the vaporizing member H. A fire screen K and a regulating damper L may be ing axially through the fire screen K. Above the latter the pipe GA is bent to extend transversely through the wall of the member GA, and thence to a suitable source of gasolene supply. In respect to its means for discharging products of heating from its combustion chamber C, the heating unit shown in Figs. 4 and 5 may be identical with that shown in Figs. 1-3.

Operatively the heating unit shown in Figs. 4 and 5 does not difier significantly from the unit shown in Figs. 1 to 3.

In Fig. 1 the outer wall A of the body A is formed with bosses A for attachment of the heating units to brackets or to other supporting parts of the airplanes in which the heating units are respectively mounted.v Each unit may advantageously be provided with a'plurality of different bosses A or analogous attachment means so that in different installations the unit may be readily attached to airplane supporting portions in different positions relative to the unit.

In Fig. 4, gasolene is supplied to the pipe GA for passage to the vaporizer I of the unit, by a small motor driven pump R, which may be in immediate proximity to the heater, so that the pipe GA is only a few inches long. As shown, the pump R draws gasolene through a pipe S from an airplane fuel supply tank T. The length of the pipe S will vary with conditions, and may be 20 feet or even greater in some cases, and

a rupture or puncture oi. the pipe by a bullet through a valve mechanism U which will close communication between the tank and pipe except when the outlet port of the valve mechanism U is subjected to the pump suction normally created by the pump R.

. The valve mechanism U may take various forms. As shown in Fig. 6, it comprises a small diameter inlet port U which is closed when the pump R. is out of operation by a check valve in the form of a ball U then held in its closed position by a short light spring U acting between the valve IF and a valve member U. The latter, when not subjected to the suction created by the pump R is held by a. spring U in the position in which it extends into and closes a port between the port U and the pipe S, which is of substantially greater cross section than the port U. The strength of the spring U is not great enough, however, toprevent the valve member U from opening and thereby permit the valve U to open when the normal pump suction is transmitted to the valve mechanism U through the pipe S.

In considering the practical protective effect of the valve mechanism U, it should be borne in mind that to pass gasolene from the heater at the bore of the pipe S may well be of the order of 0.06 of an inch.' In consequence, on severance of the pipe 8 and the resulting closure of the check valve U, the amount of gasolene "in the portion of the severed pipe running to the tank '1 will be quite small. If when the pipe S is severed the pump R remains in operation, there will be practically no leakage of gasolene out of the portion of the pipe extending from the point of severance to the pump.

Fig. 7 illustrates a modification of the apparatus shown in Figs. 4 and 5 in which the circulating fan MB is an exhaust fan driven by a motor NB, and arranged to draw the air heated through the spaces between the heat dissipating fins A from an inlet opening Q in the casing QA at the opposite side of the body AA, and to discharge the air through a transverse casing outlet Q While I consider it ordinarily preferable to use a porous ceramic body I through which gasolene is moved by capillary action to a vaporizing surface, other means may be employed. Thus, for example, as shown in Fig. 8, I may employ a body IA comprising a plurality of thin metal discs I detachably clamped together by bolts I to provide joint spaces between the laminae through which gasolene may flow by capillary action from a supply well or reservoir to vaporizing surfaces. The rate of flow through said joint spaces may be regulated by varying the clamping pressure exerted on the laminae by the bolts 1 As shown, the body IA is identical in general form with the body I, and comprises a central well IA, peripheral slots IA and through passages 1A As shown, the thickness of the central portion of the body IA is increased by metallic end parts I" which may be welded to the top and bottom laminae of the body. As shown in Fig. 8 the body IA is mounted in a heater unit oi. the form shown in Fig. 4.

As those skilled in the art will recognize, the static character of the gasolene vaporizing means shown in one form in Figs. 1 and 4 and shown in a different form in Fig. 8 contributes to the simplicity in construction, reliability in operation and'compactness and small weight of a heating unit in which such means are employed, which is especially desirable when said unit is used for airplane heating.

It will now be understood that the inner tubular wall portion A provides a heating space C which is imperforate and fluid-tight except at the inlet passages H and the outlet adjacent to the rotor E. The cup-shaped member H and combustion air conduit connection cooperating therewith form the chamber i to which air is supplied through passage G and in which vaporization of combustible fluid is effected at the surfaces of the porous block I, as described above.

The burner formed by the cup-shaped memoer H is arranged to seal the inlet of the heating space C and includes the wall member interposed between the chamber i and. heating space 0 and formed with the passages H. With this construction the only fluid flowing into the heating space C is the combustible mixture formed in the chamber 1, and this mixture is subdivided into small gas streams at the openings H which are distributed over a major portion of the cross-sectional area of the inlet of the heating space C. Substantially complete burning ofthe small gas streams issuing from the openings H into the space C is accomplished at and in the immediate vicinity of the wall member having the openings H, and only heated products of combustion pass through the space C toward the outlet after leaving the vicinity of the wall member at the inlet.

. The porous block I in the embodiment of Figs. 1 and 2 and the laminated block IA in the em bodiment of Fig. 8 are formed with central wells to the surfaces or faces of which fuel is supplied in a liquid state. Such fuel is distributed over extended surfaces which are removed from the faces of the central wells, as at surfaces formed by the radially extending slots I and IA and the openings I and 1A The fuel distributed over the extended surfaces formed by the slots and openings is picked up and mixes with combustion supporting air flowing in physical contact therewith. The apertured wall H at the inlet of the heating space C is spaced from the porous body I and receives the combustible mixture in an unburned condition. The mixture of combustion supporting air and fuel supplied to the burner desirably is a completely combustible mixture, so that substantially complete burning is effected at the upper region R of the heating space C.

While in accordance with the provisions of the statutes, I have illustrated and described the best form of embodiment of my invention now known to me, it will be apparent to those skilled in the art that changes may be made in the form of the apparatus disclosed without departing from the spirit and scope of my invention, as set forth in the following claims.

Having now described my invention, what I claim as new and desire to secure by Letters Patent, is:

l. A heater comprising a heating unit for heating a medium adapted to flow in heat exchange relation therewith, said unit including means providing a passage forming a substantially closed heating space having an inlet at one end and an outlet at its opposite end, said heating space being imperforate except at the inlet and outlet, a burner at the inlet arranged to close the latter and communicating with said heating space, structure to provide for said burnmeans providing a passage forming a heating er a mixture of combustion supporting air and fuel which is completely combustible, said structure including means for distributing fuel supplied thereto and providing an extended surface adapted to be wetted and from which fuel vaporizes and mixes with combustion supporting air flowing in physical contact therewith, means for igniting said complete mixture at said burner,

said burner including means to discharge said complete mixture into said space in a multiplicity of jets so that substantially complete burning of the jets may be accomplished at and in the immediate vicinity of said burner and substantially only heated products of combustion pass into said heating space from the vicinity of said burner at the inlet, and said heated products of combustion passing from said heating space at the outlet.

2. A heater comprising a heating unit for heating a medium adapted to flow in heat exchange relation therewith, said unit including means providing a passage forming a substantially closed heating space having an inlet at one end and an outlet at its opposite end, said heating space being imperforate except at the inlet and outlet, a burner at the inlet arranged to close the latter and communicating with said heating space, structure to provide for said burner a mixture of combustion supporting air and fuel which is completely combustible, said structure comprising material possessing such physical properties that fuel supplied thereto is readily distributed over an extended surface thereof and from which fuel is picked up and mixes with combustion supporting air flowing in physical contact therewith, means for igniting said complete air-fuel mixture at said burner, said burner receiving said complete air-fuel mixture after being formed at the extended surface of said material and including means to discharge said complete air-fue1 mixture into said space in a multiplicity of jets so that substantially complete burning of the jets may be accomplished at and in the immediate vicinity of said burner and substantially only heated products of combustion pass into said heating space from the vicinity of said burner at the inlet, and said heated products of combustion passing from said heating space at the outlet.

3. A heater comprising a heating unit for heating a medium adapted to flow in heat exchange relation therewith, said unit including means providing a passage forming a heating space having an inlet at one end and an outlet at its opposite end, structure to provide a mixture of combustion supporting gas and fuel, said structure comprising a body of material possessing such physical properties that fuel supplied to one face thereof in a liquid state is readily distributed over an extended surface removed from said face and from which surface fuel is picked up and mixes with combustion supporting gas flowing in physical contact therewith, means spaced from said body and at the inlet to receive said mixture in an unburned condition, said last-mentioned means being in communication with said heating space and providing a region in which combustion and burning of said mixture may be initiated, means for igniting said mixture at said region, and the heated products of combustion passing from said heating space at the outlet.

4. A heater comprising a heating unit for heating a medium adapted to flow in heat exchange relation therewith, said unit including space having an inlet at one end and an outlet at its opposite end, a burner at the inlet arranged to close the latter, means forming a chamber, said burner including a burner screen interposed between said chamber and said heating space, said burner screen having a plurality of small apertures constituting the sole passages for introducing combustion supporting gas into said heating space, means to supply fuel to said chamber, means within said chamber adapted to be wetted by the fuel supplied thereto and formed so as to provide a relatively extensive gas and liquid contact surface whereby fuel at said surface mixes with combustion supporting gas flowing in physical contact therewith, means to supply combustion supporting gas to said chamber to produce therein a mixture of gas and fuel which is completely combustible, said burner screen being adapted to receive said complete mixture in an unburned condition so that substantially complete burning of the subdivided gas streams issuing from said apertures may be accomplished at and in the immediate vicinity of said burner and substantially only heated products of combustion pass into said heating space from the vicinity of said burner at the inlet, and the heated products of combustion passing from said heating space at the outlet.

5. A heater comprising a heating unit for heating a medium adapted to flow in heat'exchange relation therewith, said unit including means providing a passage forming a heating space having an inlet at one end and an outlet, at its opposite end, a burner at the inlet ar-- ranged to close the latter, means forming a chamber, said burner including a burner screen interposed between said chamber and said heating space, said burner screen having a plurality of small apertures constituting the sole passages for introducing combustion supporting gas into said heating space, ignition means for said bumer, means to supply fuel to said chamber, means within said chamber for vaporizing the fuel supplied thereto, means to supply combustion supporting gas to said chamber to produce a mixture of gas and fuel which is completely combustible, said burner screen receiving said complete mixture which is subdivided into a plurality of small gas streams distributed over a major portion of the cross sectional area of the inlet that substantially complete burning of the small gas streams issuing from said apertures may be accomplished at and in the immediate vicinity of said burner and substantially only heated products of combustion pass into said heating space from the vicinity of said burner at the inlet, and the heated products of combustion passing from said heating space at the outlet.

6. A heater comprising a heating unit for heating a medium adapted to flow in heat exchange relation therewith, said unit including means providing a heating space having an inlet at one end and an outlet at an opposite end, said heating space being imperforate and fluid tight except at the inlet and outlet, means forming a chamber, means to supply fuel to said chamber, means to supply air to said chamber, means within said chamber whereby vaporization of fuel into the air may be effected to produce a combustible mixture therein, a burner arranged to seal said space at the inlet, said burner including a wall member interposed beings 111 said wall member receiving only said mixture from said chamber, and said wall membe! being imperiorate except for the openings therein which receive combustible mixture from said chamber so that the only fluid passing into said space is the combustible mixture formed in chamber which is subdivided by the openings whereby substantially complete burning o! thesmall gas streams issuing from said openings 

